DETROIT - From concept cars partially made of discarded soft-drink bottles to plant-based material used in seats and upholstery, automakers are looking at ways to make their vehicles more environmentally friendly.

While efforts to roll out more gas-saving hybrids, meet tougher fuel economy standards and cut tailpipe emissions get much of the attention, what goes into making cars is another key part of efforts to green the auto industry.

"The whole issue around sustainability is not just about fuel economy," Mark Fields, Ford Motor Co.'s president for the Americas, said after unveiling the Lincoln MKT concept touring vehicle during media previews at the North American International Auto Show. "It's being good stewards in the environment, and that means the materials that you use."

The Lincoln MKT, which partially is made of plastic bottles and polyester waste, underscores Ford's hope to commercialize greener materials and appeal to more environmentally minded drivers. It's part of increasing attention industrywide to the overall environmental impact of vehicles.

But unlike Toyota Motor Corp.'s gas-sipping hybrid Prius, which offers drivers instant recognition for buying an environmentally friendly vehicle, car bodies made out of recycled materials and interiors that feature plant-based fabrics aren't easily noticeable to buyers, if at all.

"It's an open question whether people are willing to pay more," said Jack Nerad, executive market analyst for Irvine, Calif.-based Kelley Blue Book, who noted such offerings typically come at a premium. "A lot of people want this kind of thing, as they want better fuel economy, but they are not willing to pay more."

It may be more difficult than selling a hybrid, but Nerad said automakers should be able to market these materials to buyers.

"Prius makes a statement about the people who drive them," Nerad said, "so there is this brand opportunity as people are more aware."